234 



BRITISH FLOWERING PLANTS 



they are fleshy. In Silyhum marianum the involucre 

 contracts, compressing the achenes more and more until 

 at last they detach themselves and are scattered in all 

 directions. The common Calendula (Marigold) of our 

 gardens is a very interesting case. Three devices for 

 dispersal are united in each head. The outer achenes 

 (Fig. 153) are narrow, and bent into a curve forming 

 three parts of a circle, and well adapted to hang on to 



Front view. 



Section. 



Hooked form. Winged form. Grub-lilce form. 



Fig. 163. Fig. 154. Fig. 155. 



Figs. 153-155. — Seeds of Calendula officinalis, showing various forms. 



the hair of any passing animal. Then follow a certain 

 number which are puffed out with wide wings (Fig. 

 154), and are evidently intended for dispersal by wind. 

 Towards the centre the achenes are smaller, and much 

 resemble small green or brown caterpillars (Fig. 155). 

 These, it has been suggested, are picked up by birds, 

 and then dropped when they discover their mistake. 

 Between the extreme types there are many intermediate 

 forms. 



